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.Dd November 17, 2014
.Dt VN_LOCK 9
.Os
.Sh NAME
.Nm vn_lock ,
.Nm vn_unlock ,
.Nm vn_islocked
.Nd serialize access to a vnode
.Sh SYNOPSIS
.In sys/vnode.h
.Ft int
.Fn vn_lock "struct vnode *vp" "int flags"
.Ft void
.Fn vn_unlock "struct vnode *vp"
.Ft int
.Fn vn_islocked "struct vnode *vp"
.Sh DESCRIPTION
These calls are used to serialize access to the filesystem, such as
to prevent two writes to the same file from happening at the
same time.
.Pp
The arguments are:
.Bl -tag -width flags
.It Fa vp
the vnode being locked or unlocked
.It Fa flags
One of the lock request types:
.Bl -column ".Dv LK_FAILRECLAIM" -offset indent
.It Dv LK_RETRY Ta "Automatically retry on timeout"
.It Dv LK_FAILRECLAIM Ta "Fail if the vnode is being reclaimed"
.El
.El
.Pp
The
.Fn vn_lock
function will require either
.Dv LK_EXCLUSIVE
or
.Dv LK_SHARED
to be
.Em or Ns 'ed
with the request flags described above in order to specify the type
of lock to be used.
.Pp
The
.Fn vn_unlock
function uses
.Dv LK_RELEASE
internally to release a previously held lock.
.Pp
Please note all these functions rely on
.Xr lockmgr 9
to perform their operations.
.Sh RETURN VALUES
The
.Fn vn_lock
function returns zero on success and non-zero on failure.
.Pp
The
.Fn vn_islocked
function has identical return values as
.Xr lockstatus 9 .
.Sh SEE ALSO
.Xr lockmgr 9 ,
.Xr vnode 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .